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Patented Jan. l, 1929.

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CHARLES HILAIRE HENR RODANET, OF VERSAILLES, FRANCE, ASSIGNOR TO SOCETE ANONYME ETABLISSEMENTS ED. JAEGER, F LEVALLOIS, FRANCE, A COMPANY OF FRANCE.

ELECTRICAL MEASUBING APPARATUS.

Application filed March 17, 1927, Serial No. 1726,217, and in France March 19, 1926.

This invention relates to improvements in the construction or' electrical measuring apparatus, and more particularly in the construction of amn'ieters. lmportant features of the present invention are the special mounting and form of the indicating needle or pointer, land the Vspecial devices adopted to ensure a strong precise apparatus, 'capable of being made by repetition work. In its preferred form the casing ot the apparatus comprises interiorly two partitions and a boss diametrically opposed. and presenting parallel grooves or Uaps in which the extremities of a laminated core, surrounded by a coil connected to the control circuit, engage. The boss is formed with lateral housings for the poles of an annular permanentmagnet, also a housing for the members serving as bearings for one of the extremities of the axle of the needle, and also a sector-shaped compartment. The members serving as bearings for the other end of the needle axle are constituted by a plate and a bridge piece secured to the said boss. The sector-shaped compartment receives two blades formed on the lower limb of the needle and Set perpendicularly to itsV plane, which in conjunction with the sectorshaped compartment constitutea damping system for the movable elements.

i Solid with the axle of the needle is an arma# ture. A feature of the constructional arrangement above described is that the axis or centre of gravity of the needle armature coincides with the point of crossing` of the polar axis of the permanent magnet with the vertical axis of the laminated core of the coil, the consequence being that the needle is extremely sensitive.

The preferred embodiment of the above features of novelty will now be described more fully with reference to the accompanying drawings in which Figures 1 and 2 arc respectively a front elevation, and a vertical. cross section of apparatus iu .accordance with the present invention.

Figure S is a perspective view on a larger s fale, partly in section.

The cylindrical casing 1 of the apparatus is formed or provided internally in its upper part with two converging partitions 2 and in its lower part with a trapezium-shaped boss 3, the two converging sides of which are situated in the diametric planes containing respectively the two partit-ions 2. The casing l also comprises three internal bosses 4 for receiving the ixing screws 5 of a glass cover trame 6 which serves to close the said casing 1.

The transverse partitions 2 are each provided with a shoulder piece 7 outwardly inclined with respect to thedepth of the casing. rlhe trapeziunrshaped boss 3 has formed on the shorter oi'iits parallel faces a groove 8 of rectangular section, also outwardly inclined. On the two converging sides of the boss dare formed cylindrical housings 9 to receive the ends or poles of an annular permanent polarized magnet- 21. The boss 3 is also formed with a truncated conical recess or bore 10 surmounting a sector-shaped compartment 11.

The top and bottom ends of an assembly or sheets 12 or' a laminated core are housed re-A spectively in a gap or groove between thefree Y ends of the shoulder pieces 7 ot the partitions 2 and in the groove 8 of the boss 3, the bottom end of each sheet beingcomposed of a triangular portion and a horizontal extension or shoe 13. The laminated core is surrounded by a sleeve 14 of insulating material (bakeliZ-ed cardboard for example). The extremities of the sleeve 14 lit into or against upper and lower insulating washers 15 bearing respectively against the shoulder pieces 7 and the shoes 13 of the sheets 12 of the core.

Between the washers 15 an insulating plate 16 is held on the bottom of the casing 1. This plate 16 is fastened in place by means of fixing bolts 17, which pass through the bottom of the casing 1 and serve on the inside of the casing as terminals 18, and on the outside of the casing engage connecting leads 19, permitting the connection of the apparatus with the general circuit which controls it. The terminals 18 receive the ends of an insulated wire 20 which forms the coil around the laminated core.

In the truncated bore 10 located between the poles of the permanent magnet 21 is mounted a movable armature carrying t-he indicating needle or pointer 24. The armature is composed of juxtaposed'sheets 22 integral with the axle 23 of the needle 24, the latter being fixed between the front pair of the sheets 22. The needle 24 is cut from a metal plate and has, onl its lower limb two blades 25 Which .arefolded back at right angles to form a kind of U-shaped member. This member oscllates during angular movements of the needle 24, in the sector-shaped compartment 11 formed. in the boss 8. rIhis in its entirety tormsan air damper.

The axle 23 of the needle 24 is mounted on pivots like those used in clockwork. For this purpose each of its pivot forming extremities passes through the central bore of a mounting member and rests on a jeivelledV counter-pivot member 27. The rear mounting,` memberor guide 26 and its counterfpivot member 27 are lodged in the truncated oor l0. The other mountingmember or guide and its corresponding counter-pivot member are constituted respectively by a vplate 28 and a bridge piece 29, which are assembled in juxtaposition on theV boss 3.

A sector 30, of transparent material, permitting the adjustment of the damping system of the rneedle 24e closes the'compartment 1l.

The casing 1 is closed by the dial 3l. and is provided with a dial trame 6 With glass 'tace 82, completing the apparatus.

What I claim is :m-

`1. In an electrical measuring instrument suoli as anammeter, involving` the presence of a magnet and an indicating needle, the latter ,having an armature, a casing having an internal boss, said boss being recessed laterally to lreceive the polar ends oit the magnetand said casing being formed adjacent said boss inlaibore in which the needle axle and its armature are enclosed.

2. In an electrical measuring instrument such as an ammeter, a casing, a permanent annular magnet therein, a cnrrentfearrying coil and ilaminatedfcore set with their axial plane crossing the polar axis of said magnet, a pivoted indicating needle :having its axle coincident with theintersection of the aforesaidaxiaLplaneand polar axis, an armature solid with said axle, two `internal ypartitions inithe casing presenting at their free ends a plane crossing/the Apolar axisot said magnet,

a pivoted indicating` needle having itsv axle coincident nithithe intersection oftliegajforesaidaxial yplane and polar axis, an armature solid With said axle, tivo internal partitions in the casing presenting at their tree ends a gap to house the upper end of the coil snrrounded core, rand av diametrically opposite internal boss .having a ,groove to house the lower endet the said core, said -boss having a here in lwhich the needle axleand its armature are enclosed..

4i. In electrical'measuring instrument auch as an ammeter, a casing, a ypermanent annular magnet therein, a current-carrying coil and laminated core set with-their axial plane crossing` the polar axis of said magnet, a fpivoted indicating needle `having` its axle coincident with the intersection ot the aioresaid axial plane and polar axis, an armature solid With said axle, anextension of the indicating needle beyond its axis of rotation, two internal partitions inl-the casing` presentingat their -free'ends a gapftohouse the npper-end of the oo il surrounded core, ,a dian ietricalljT opposite internal boss having a groove to house `:the lower lend kof the `said core, and an annnlar chamber xinthe shape of a cylindrical -seetor .cooperating with Ethe Said extension ,0f ,the indicating A166011@ ,t0 constitute anairdamper.

`In Vtestimonv iivhereof I have signed my name to this specification- 

